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Holes in GPS

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Created by Macroscien Saturday, 30 Nov 2019
Macroscien
QLD, 4787 posts
Saturday , 30 Nov 2019 7:44PM
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Is it me only or most common? Recently my logs comes with up to 30 minutes holes.GPS GW 60

30 Nov



26 November
apparently another sailor , same place, same time experienced even worse reading

What do cause the problem? Are we preparing for WWIII or UFO just landed near by recently?
Luckily we are not yet at the stage of self sailing autonomously windsurfing boards. Could crash for sure or make a good dip towards New Zealand with such navigation.
third sailor at same place

then Brisbane 60 km away affected too

But suprasingly Lake Cootharaba ( 300km ) wasn't yet invaded by Aliens !? or just single hit at 3pm exactly

Yep, story becomes more and more fascinating. The most probable explanation is that Earht was hit by wormhole ( Time shifting device/phenomenon) that cause Y2K problem appear suddenly after 20 years past.


www.abc.net.au/news/2019-04-10/weather-balloons-grounded-in-gps-clock-rollover-glitch/10984806






decrepit
WA, 9636 posts
Saturday , 30 Nov 2019 6:34PM
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poor sat coverage on the Eastern states. If you change the filters to say 4 sats instead of the default 5. I predict those holes will get smaller.
The dater is probably there, but the filters are preventing the from displaying. Although looking at the green line, (the sat numbers), that bad period of yours has periods with no reception at all.

And the bottom display is still showing mainly 5 sats. Looks more like he was having a rest. You'll notice he has a thick black line at the bottom. you don't.

The thing with the watch with it's smaller antenna and wrist mount it's often not in the best position for good reception. Not using the underhand grip will improve things, but probably not enough in your case.

It can also be instructive to turn on SDoP when looking at this stuff.

sailquik
VIC, 4772 posts
Saturday , 1 Dec 2019 12:26AM
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This is particularly and issue with the GW-60 becasue of the way it is worn on the wrist and is often in underhand grip (all watch type GPS will probably have this issue).

Here are the satellite visibility/availability charts for 28/29th Nov at Wellington Point, Qld.

Note that with the elevation mask set at an optimistic 10 degrees, there is still a maximum of 5 or 6 sats that should be available for the early afternoon. But some of those could be very weak (low in the sky)
.



But notice also that if we raise the elevation mask to 20 degrees (above the horizon), it gets a LOT more problematical for a much greater period of time. Any of the yellow period is likely to be an issue:




The best advice I can give, if you know there is low satellite availability, is to try to avoid underhand grip, or to wear your GW-60 on a different part of you body so that the antenna has a better sky view.

Generally speaking, we dont see this issue with the GT-31 as it has a larger antenna, and is usually worn on the upper arm where it usually has a better sky view. The same applies to the GW-52 because it too is usually worn the same way.

This is also a big reason why the Motion GPS is a big step forward. It is Multi-GNSS. That means it can use the satellites from two (or even 3) seperate systems. Ie, GPS plus another (usually Glonass or Gallileo). AND, it is worn on the uper arm. So a situation with an inadequate number of satellites for a very good solution (fix) is extremly unlikely to arise.

Cocky2
QLD, 160 posts
Sunday , 1 Dec 2019 9:10AM
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Select to expand quote
sailquik said..
This is particularly and issue with the GW-60 becasue of the way it is worn on the wrist and is often in underhand grip (all watch type GPS will probably have this issue).

Here are the satellite visibility/availability charts for 28/29th Nov at Wellington Point, Qld.

Note that with the elevation mask set at an optimistic 10 degrees, there is still a maximum of 5 or 6 sats that should be available for the early afternoon. But some of those could be very weak (low in the sky)
.



But notice also that if we raise the elevation mask to 20 degrees (above the horizon), it gets a LOT more problematical for a much greater period of time. Any of the yellow period is likely to be an issue:




The best advice I can give, if you know there is low satellite availability, is to try to avoid underhand grip, or to wear your GW-60 on a different part of you body so that the antenna has a better sky view.

Generally speaking, we dont see this issue with the GT-31 as it has a larger antenna, and is usually worn on the upper arm where it usually has a better sky view. The same applies to the GW-52 because it too is usually worn the same way.

This is also a big reason why the Motion GPS is a big step forward. It is Multi-GNSS. That means it can use the satellites from two (or even 3) seperate systems. Ie, GPS plus another (usually Glonass or Gallileo). AND, it is worn on the uper arm. So a situation with an inadequate number of satellites for a very good solution (fix) is extremly unlikely to arise.



Motion has been a 8 month wait for people since ordering. Still not an option readily available.

sailquik
VIC, 4772 posts
Sunday , 1 Dec 2019 3:26PM
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Select to expand quote
Cocky2 said..



sailquik said..
This is particularly and issue with the GW-60 becasue of the way it is worn on the wrist and is often in underhand grip (all watch type GPS will probably have this issue).

Here are the satellite visibility/availability charts for 28/29th Nov at Wellington Point, Qld.

Note that with the elevation mask set at an optimistic 10 degrees, there is still a maximum of 5 or 6 sats that should be available for the early afternoon. But some of those could be very weak (low in the sky)
.



But notice also that if we raise the elevation mask to 20 degrees (above the horizon), it gets a LOT more problematical for a much greater period of time. Any of the yellow period is likely to be an issue:




The best advice I can give, if you know there is low satellite availability, is to try to avoid underhand grip, or to wear your GW-60 on a different part of you body so that the antenna has a better sky view.

Generally speaking, we dont see this issue with the GT-31 as it has a larger antenna, and is usually worn on the upper arm where it usually has a better sky view. The same applies to the GW-52 because it too is usually worn the same way.

This is also a big reason why the Motion GPS is a big step forward. It is Multi-GNSS. That means it can use the satellites from two (or even 3) seperate systems. Ie, GPS plus another (usually Glonass or Gallileo). AND, it is worn on the uper arm. So a situation with an inadequate number of satellites for a very good solution (fix) is extremly unlikely to arise.






Motion has been a 8 month wait for people since ordering. Still not an option readily available.




The fact is that the Motion is still currently the best out there. Good things come to those with patience.

If you can't wait, the GW-60 is still the best of the rest keeping in mind what is written above.

Nothing will ever be perfect for all people.

tbwonder
NSW, 233 posts
Monday , 2 Dec 2019 10:26PM
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Here is an example from Budgie today. I was using my GW60 and Motion. The GW60 missed my best run of the day (40.1kts) but fortunately the Motion saved the day.


decrepit
WA, 9636 posts
Monday , 2 Dec 2019 9:53PM
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Interesting that the GW60 even with missing sats, had a very similar looking graph.
So was that an underhand grip on the down wind run? Looks like you lost reception as you went downwind, and got it back as the run finished

tbwonder
NSW, 233 posts
Tuesday , 3 Dec 2019 7:23AM
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Select to expand quote
decrepit said..
Interesting that the GW60 even with missing sats, had a very similar looking graph.
So was that an underhand grip on the down wind run? Looks like you lost reception as you went downwind, and got it back as the run finished



No the GW60 was on my back (left) wrist which would have been facing upwards.

sailquik
VIC, 4772 posts
Tuesday , 3 Dec 2019 8:20AM
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previous post deleted due to incorrect UTC time. This one should be correct:





tbwonder
NSW, 233 posts
Tuesday , 3 Dec 2019 8:55AM
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Be careful with your time zones Daffy, those graph you posted are for GMT. We are 11 hours ahead so right in that nasty yellow patch. My run was at 3:44 pm NSW time


sailquik
VIC, 4772 posts
Tuesday , 3 Dec 2019 10:03AM
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Select to expand quote
tbwonder said..
Be careful with your time zones Daffy, those graph you posted are for GMT. We are 11 hours ahead so right in that nasty yellow patch. My run was at 3:44 pm NSW time







Ahhhhh!!! Stuffed up again!

Sat availability table corrected. But it does look like there should have been OK availability at the time of your run. And if the GPS was overgip, something else must be at play on this track. It's a bit of a mystery........

Ezric
NSW, 181 posts
Tuesday , 3 Dec 2019 5:25PM
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I have had the same issue a couple of times recently. On the most recent occasion, I spoke with other sailors as it happened, three GW60's and two GT-31's lost signal at the same time(just after 4pm NSW), regardless of orientation. It lasted about 20 minutes then all devices worked fine again for the rest of the days sailing.

decrepit
WA, 9636 posts
Tuesday , 3 Dec 2019 3:12PM
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Ah well if the GT31 lost signal, the GW60 would have no hope.

sailquik
VIC, 4772 posts
Tuesday , 3 Dec 2019 6:39PM
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Hmmm..... I wonder if some bad Foriegn State actor is meddling with the GPS system, as part of a nefarious plot to undermine the GPS-TC?

tbwonder
NSW, 233 posts
Tuesday , 3 Dec 2019 10:50PM
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Today I put a GT 31 on the roof at home for 10 hours from midday until 10pm (NSW Daylight saving time, GMT +11 hours). I then exported the satellite data from Real speed into Excel and then superimposed this data (The blue line) on to the Satellite prediction chart. The funny thing is to make it align I had to shift it 2 hours. So it looks like a predicted time of 2PM equates to an actual time of 4PM.
This is really confusing. Daffy can you figure this out?


decrepit
WA, 9636 posts
Tuesday , 3 Dec 2019 8:39PM
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wow, great experiment. But a very strange result.

sailquik
VIC, 4772 posts
Wednesday , 4 Dec 2019 7:50PM
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It beats me!
on the face of it, it looks like an error in the time zone offset calculation, but that would be very surprising.
I have however, forwarded your results to Navcom support to see what they say about it.

Boombuster
QLD, 517 posts
Thursday , 5 Dec 2019 7:18AM
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Seen dropouts on my GW-60 in the past but it's become worse lately it's not the devices

olskool
QLD, 1579 posts
Thursday , 5 Dec 2019 10:00AM
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Military intervention.



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"Holes in GPS" started by Macroscien